Lights Out at 10pm: All You Need To Know

One million candles will be lit tonight to commemorate the start of World War One.

Exactly 100 years ago at 10pm, the Declaration of War was signed by Foreign Secretary Sir Edward Grey, who famously remarked: "The lamps are going out all over Europe; we shall not see them lit again in our lifetime."

The service at Westminster Abbey will see candles going out one by one from 10pm until just one oil-burning lamp remains at the Grave of the Unknown Warrior. This will then be extinguished by the Duchess of Cornwall at 11pm, the exact time the British Empire joined the First World War.

It is the centre of the 'Lights Out' campaign, where people are being asked to turn off their lights from 10pm and light a single candle to remember those to gave their lives.

Major landmarks across the capital, including Westminster Abbey, Houses of Parliament, Tower Bridge and the famous lights at Piccadilly Circus, will go dark for an hour tonight.

The organisers wrote: "Everyone in the UK is invited to take part in LIGHTS OUT by turning off their lights from 10pm to 11pm on 4 August, leaving on a single light or candle for a shared moment of reflection.

"People can take part in whatever way they choose, marking the centenary of the outbreak of the First World War either individually or by attending one of the many events being organised around the country for a collective experience."

Following the declaration, four years of war followed with around six million men in the UK mobilised. More than 700,000 Britons died.